Extruding the camera block for my phone model
Here is an edit of your object with a more detailed topology (ngons at minimum, and you can easily replace them with quads, preferably, if you need to subdivide those faces).

It is not finished and it has a n X mirror modifier, but you can see that the "camera block" is quite easy to do now, and (after applying the X mirror, maybe) also side buttons, with a regular manual subdivision with CTRLR.



Here is the .blend file. Hth.